Brainstem Flashcards
What are the general functions of the brainstem?
Conduit
Allows ascending and descending pathways to reach thalamus and cerebellum from spinal cord
Relay nuclei
Integrative
Control of cardiovascular, respiratory and consciousness (reticular formation)
Complex motor patterns (e.g. balance)
Cranial nerve Head’s equivalent to spinal nerves Also sight, hearing, equilibrium and gustation Cranial nerve nuclei Reflex centers
What is the brainstem? How is it related to other structures rostrally, caudally, ventrally and dorsally?
Structure: Midbrain; Pons; Medulla oblongata
Rostrally – Midbrain is continuous with the diencephalon (thalamus, hypothalamus etc)
Caudally – Medulla is continuous with the spinal cord at level of the foramen magnum
Ventrally – Clivus of occipital bone
Dorsally – Cerebellum
Which Cranial nerves are part of the PNS?
CN: 3-12
•10 of 12 Cranial nerves arise from the brainstem – these are part of the PNS. These nerves have sensory and motor parts.
What is the Tectum?
Found posterior to ventricular system
Only region with substantial tectum (roof) is the midbrain – superior and inferior colliculi
What is the Tegmentum?
found anterior to ventricular system
contains cranial nerve nuclei and tracts, reticular formation and some ascending/descending pathways
What is the Basal layer?
most anteriorly
descending fibres from cerebral cortex (pyramids, cerebral peduncles)
What can you see in the ventral view of the Medulla oblongata?
Two pyramids
Separated by the anterior median fissure (Interrupted at the decussation of pyramids)
Contain descending motor fibres
Anterolateral sulcus separates pyramids from olives
Hypoglossal nerves emerge here
Posterolateral sulcus emerges dorsal to olive
Vagus and glossopharyngeal nerves emerge here
What can you see in the dorsal view of the Medulla oblongata?
Viewed after removal of the cerebellum
Reveals the IVth ventricle
Central canal opens into IV ventricle at obex
IVth ventricle divides the medulla into:
Open (rostral) – IVth ventricle
Closed (caudal) – central canal
Floor of the IVth ventricle – Rhomboid fossa
Either side of midline – gracile fascicle (GF)
Forms a swelling rostrally – gracile tubercle
Lateral to gracile fascicle – cuneate fascicle (CT)
Forms a swelling rostrally – cuneate tubercle
Gracile and cuneate are Part of dorsal column pathway – sensory information (from body to brain)
What separates the medulla from the pons?
pontomedullary junction
What can you see in the ventral view of the Pons?
Cerebellopontine angle (Where medulla and pons join cerebellum laterally)
Facial and vestibulocochlear emerge here
Abducens from pontomedullary junction
Trigeminal nerve enters at mid-pontine level
Midline groove for basilar artery
What can you see in the dorsal view of the Pons?
Main feature on dorsal view – cerebellar peduncles
Superior: connects midbrain to cerebellum
Middle: connects pons to cerebellum
Inferior: connects medulla to cerebellum
Superior cerebellar peduncle forms roof of IVth ventricle
What can you see in the anterior view of the midbrain?
Main feature – cerebral peduncle (basis pedunculi)
Separated by interpeduncular fossa
Oculomotor nerve emerges
What can you see in the dorsal view of the midbrain?
Main features: Paired superior and inferior colliculi
four bumps
Superior – associated with visual pathway
Inferior – associated with auditory pathway
Inferior to inferior colliculi and at junction with pons
Trochlear nerve
Only nerve to emerge from dorsal surface
Has the cerebral aquaduct (Caq) running through it
What is Reticular formation?
A complex, multisynaptic network of neurons within the tegmentum of the brainstem
Includes:
Reticular nuclei – give rise to a descending motor pathway (reticulospinal tract, see Term 3)
Vital autonomic centres – eg. respiratory, cardiovascular
Cells giving rise to Ascending Reticular Activating System – pass to the cortex and involved in consciousness (damage = coma)
Pain modulation
Sleep wake cycle
Arousal
What is the Cerebellum?
The cerebellum, or little brain, primarily involved in movement
Found under the occipital lobes of the cerebral hemispheres and
dorsal to the brainstem.
Attached to the brainstem by three paired cerebellar
peduncles: superior (to midbrain), middle (to pons) and inferior (to medulla)
